How to disable default alt-left / alt-right keyboard shortcuts for Numbers.app

I'm continually hitting Alt+Left Arrow to move navigate within a cell in Numbers, and inadvertently inserting new rows.. How can I disable all the Alt+Arrow shortcuts?

I've tried changing the Application specific keys in System Prefs > Keyboard, and my new keys work, but the old remain active. Is there a tidy oneliner to paste into the terminal?!

Edit:

Hmm.. I can't replicate the problem that I'm asking about! ATM when I Alt+Enter into a cell to edit, Alt+Left Arrow is not adding a column! Maybe I'm mashing some other keys in there intermittently?

BTW, I've also tried setting Alt+Left Arrow to Bring All Windows to Front but that disabled using Alt whilst editing the cell.

You can edit the plist directly:

defaults write com.apple.iWork.Numbers NSUserKeyEquivalents '{"Add Column Before"="\0";"Add Column After"="\0";}'

It overwrites custom shortcuts set in System Preferences, but you could also edit the plist in a text editor after converting it to XML:

plutil -convert xml1 ~/Library/Preferences/com.apple.iWork.Numbers.plist